Wireless charging is convenient because it removes the need for wires and connectors. For instance, wireless charging using RF power transmission does not require a device being charged to be placed at a fixed location or be tethered to a fixed power outlet by wire.
In a wireless charging system, a master unit can be used to transmit power to a slave device. To optimize power delivery, the location of the slave device receiving power relative to the master unit transmitting power needs to be taken into consideration. For example, the electromagnetic fields surrounding one or more antennas of the master unit can be divided into a near-field region and a far-field region. In the far-field region, the radiation pattern of the antennas stays relatively constant with respect to distance. When the slave device is located in the far-field region of the antennas, the antennas can focus a beam toward the slave device. However, as the slave device moves closer to the master unit, it enters the near-field region. Without proper adjustment to the antenna configuration, the far-field radiation pattern formed by the far-field antenna configuration may not achieve optimal power delivery when the slave device moves into the near-field region. For example, some of the antennas used to form far-field radiation patterns may not be useful to form near-field radiation patterns, thus wasting energy and computing resources of the master unit.
Thus, there is need in the art to provide a master unit that can dynamically configure its antennas to adjust its radiation pattern based on the location of a slave device to optimize power delivery in a wireless charging system.